Identification systems relying on radio frequency-based communication between a reader and a transponder or tag of various types for identifying animals and objects are in use for a number of applications. Generally, identification systems having a tag that generates an identification ("ID") signal simultaneous to its being energized by an electro-magnetic field produced by a reader are termed "full-duplex" systems. Alternatively, a "half duplex" identification system utilizes a tag capable of receiving a transmitted "charging" signal which is utilized by the tag to charge a capacitor or power storage element. The stored energy of the capacitor or power storage element can then be used to power the tag and allow the broadcast of a signal from the tag to the reader, which is in a "silent" or non-broadcasting mode. For either of the foregoing identification systems, the tags are very small, although as a general rule a full-duplex tag will be smaller than a half-duplex tag since a power storage element is required in the latter.
The tag for the identification system generally includes a memory element coupled to an antenna such as an inductive coil which facilitates coupling with an inductive power supply. The reader usually includes a battery power supply and a field coil. The coil is driven by driving circuitry that causes the coil to transmit an electromagnetic field to the tag. The field is received by the tag and converted through induction to a direct current power supply signal to run the tag circuitry in a full-duplex tag, or stored in the capacitor of a half-duplex tag. In response to the reader, the tag transmits the identification data to the reader from the tag memory, and the reader can display the data. These identification systems thus permit powering an identification tag transponder by an electromagnetically coupled energizer reader, and the transmission of an ID signal, or modification of the field of the reader coil, by the tag.
Manufacturers have developed a number of different protocols by which readers and transponders communicate the identification data. In order to read the various protocols with a single reader, a need exists for a reader capable of reading multiple tags having differing protocols which minimizes any delay associated with identifying a specific transponder protocol.